This study will examine the construct validity of personality disorders (PDs) by combining methods developed for studying the social psychology of person perception with laboratory performance measures, structured interviews, and real world data regarding social and occupational functioning. Current knowledge regarding PDs relies almost exclusively on self-report measures (questionnaires and interviews). Unfortunately, people with PDs are frequently unable to view themselves realistically and unaware of the effect their behavior has on other people. Our study compares information regarding pathological personality traits from self-report measures with peer nominations made by people who are well-acquainted with each other. Participants are groups of men and women who completed basic military training together (2,100 Air Force recruits) or who have lived together in a college dormitory (1,200 first-year students). We have shown that peer judgments regarding pathological traits are reliable and valid and that our sample includes a substantial number of people who meet DSM-IV criteria for at least one PD. We have also found that correlations between self-report and peer-report measures range from .20 to .30. In the next five years, we will pursue these findings to compare the validity of self-report and peer-based measures. Our extensive data set will also be used to examine related issues such as gender bias in diagnostic criterion sets. Follow-up information will be collected using electronic personnel databases (for AF recruits) and performance on laboratory tasks (for college students). These data will allow us to evaluate the impact of pathological personality traits on functional outcomes in people's lives. We will also develop assessment procedures that can be used to supplement traditional self-report instruments.